The present invention relates generally to spraying systems, and more particularly, to spraying systems in which the supply liquid, in part, is recirculated during the spraying operation.
When spraying thixotropic liquids which have a tendency to crystallize or solidify, such as liquid chocolate, the supply liquid must be heated and recirculated during the spraying operation so that the liquid stays above a crystallization temperature and remains in motion at all times. If the liquid dead-ends at the nozzle or spray header, and hence ceases to circulate, clogging is likely to occur.
Typically, the supply liquid is provided in an open tank from which it is pumped to the spray nozzle or header. Excess liquid that proceeds past the spray nozzle or header is returned back to the open tank for reuse. Such system is disadvantageous because the pumps are relatively expensive and difficult to heat. It also is difficult to inexpensively control the pressurized liquid supply in such system. In some instances, the supply liquid is provided in a pressurized supply tank. Pressure in the tank directs the liquid to the spray nozzle or header, with excess liquid being returned to an open tank. In this case, the return liquid must be poured into the existing or a new pressurizable supply tank. This repeating procedure can be tedious, time consuming, and disruptive of the spraying operation.
It is an object of the present invention to provide a spraying apparatus with a liquid supply and circulation system, particularly adapted for use with thixotropic liquids, which eliminates both costly pumps and the tedious handling of return liquid from the spray nozzle or header.
Another object is to provide a spraying apparatus with a liquid supply and circulation system as characterized above which can be operated on a substantially uninterrupted basis.
A further object is to provide a spraying apparatus with a liquid supply and circulation system of the foregoing type in which the return liquid may be redirected to the spray nozzle or header without significant interruption in the spray operation.
Still another object is to provide a spraying apparatus with a liquid supply and circulation system of the above kind which includes a plurality of pressurizable liquid supply and liquid return tanks which can be alternatively and successively used for supplying pressurized liquid to the spray nozzle or header without substantial interruption in the spraying operation.
Yet a further object is to provide a novel method of supplying liquid to a spray head utilizing a multiplicity of pressurizable liquid containable tanks.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which: